RS53932B1 - ELECTRICAL GENERATOR - Google Patents

Abstract

An electrical generator powered by an external energy source, such as wind, comprising: - a drive shaft (3) with a longitudinal shaft (L), designed to be connected to an external energy source and having a predetermined torque; rotary electric machines (7) with synchronous resistance consisting of a stator (8) and a transverse laminated rotor (9), and an ejected shaft (6) operably coupled to said drive shaft (3) to generate electricity with a torque of a predetermined amplitude during operation; - electrical means (13) for injecting into the network (R) electricity generated by said electric machine (7); - control means (14) designed to adjust the electrical and dynamic parameters of said electrical machine (7); said stator (8) has an even number (ns) of longitudinal grooves (15) for each pair of bars, and said stator (9) has a plurality of longitudinal slots (16) defining an even number ( nr) magnetically equivalent slots, characterized in that said number (ns) of grooves (15) is different from the number (nr) of equivalent slots multiplied by an integer (m), where is the difference between said number (ns) of grooves and said number ( nr) equivalent slots other than zero, +2 and -2, wherein said rotor (9) is formed by a plurality of disk plate elements (17) arranged longitudinally side by side, wherein said plurality of longitudinal slots (16) are provided for passage where each forms in each of the plurality of elements a disk plate (17), wherein each of said elements a disk plate (17) is substantially annular, with an outer diameter (D) and a central through hole inside the diameter (d) designed to be connected to said ejected shaft (6), wherein the ratio (r) between said inner diameter (d) and said outer diameter (D) of each annular element of the disk plate (17) is between 0.4 and 0.8. The application contains 7 more claims .

Description

Field of invention

The present invention finds application in the field of electric machines, in particular it relates to an electric power generator with a drive that comes from an external energy source, especially a renewable type, such as wind as an energy source.

State of the art

Generators are known to consist of a rotating electrical machine having a stator and a rotor connected to a drive shaft, which is driven by an external energy source, for example an alternative energy source, such as wind as an energy source, or hydraulic or chemical energy sources.

Furthermore, the generator consists of control means for adjusting the electrical and dynamic parameters of the electrical machine and electrical connection means for injecting electrical energy into the supply network or into electrical storage means, such as electrical battery units.

A special type of electric generator consists of double-charged asynchronous electric machines, in which the stator is connected to the external mains and the rotor is electrically connected to the means for adjusting the magnetic field connected thereto.

The control means can adjust the speed of rotation of the rotor and maintain it at a predetermined value, so that the electricity injected into the grid has an essentially constant, predetermined current.

In general, the electric rotating machine in the double charging generator is an asynchronous electric machine that is used as a generator.

While this type of electric machine has a solid structure and especially has advantages in terms of cost, it still has certain disadvantages.

The first disadvantage is that asynchronous machines have significantly large dimensions and are very heavy, especially when connected to an electric generator of medium to high power, e.g. 500 kW generators.

The next disadvantage is that these machines have non-negligible electrical losses, which significantly reduce the efficiency of the generator.

In an attempt to at least partially eliminate these defects, electric generators have been developed, so that they use rotating electric machines with permanent magnets. Unlike the previous configuration, the electrical control means of these generators include a first electrical connection to the stator windings and a second electrical connection to the external grid.

Overall, generators with permanent magnet electric machines provide advantages compared to asynchronous generators, such as lower magnetic losses and smaller dimensions and weight.

Even so, permanent magnet machines have higher costs than dual charge asynchronous machines.

Furthermore, with permanent magnet machines, the amount of current delivered increases in an essentially linear fashion with increasing rotor speed.

Accordingly, in order to maintain the delivered current at an essentially constant value, the machine must be defluxed, that is, the existing magnetic field flux must be reduced as the speed of rotation of the electrical machine changes.

For this purpose, the control means operate on the machine by injecting an electric current which has such a direction as to generate a magnetic flux opposite to that generated by the permanent magnets.

A particular disadvantage of this solution is that, especially under operating conditions, the defluxing current can have a high value and require exaggerated control means.

Furthermore, in certain passages, defluxing can cause higher electrical losses from the windings of the electrical machine, due to the Joule effect.

Electric generators using synchronous electric machines are known. For example, EP0156606 refers to a similar generator consisting of a synchronous-resistance electric machine having a laminated rotor.

Document JP 2008 48584 also refers to a similar generator.

However, these prior art machines have very low electrical efficiency and are also characterized by large torque oscillations.

Description of the invention

The main object of the present invention is to overcome the above disadvantages by providing a generator which is highly efficient and relatively cost effective.

A special object is to provide a generator consisting of a rotating electrical machine that has particularly high performance and low electrical losses.

A further particular object is to provide a generator whose cost is significantly lower than a conventional rotating electric machine generator having permanent magnets.

Another special object is to provide a generator that is smaller in size and weight, even for medium to high current applications.

It is a further particular object of the invention to provide a generator which utilizes a non-exaggerated electric machine.

Another particular object of the invention is to provide a generator having electrical adjustment means with lower electrical and current specifications than electrical adjustment means of generators consisting of rotating permanent magnet electric machines.

A further important particular object of the present invention is to provide a generator having control means of smaller dimensions and weight compared to means of electrical adjustment of generators consisting of rotating electric machines with permanent magnets.

These and other objects, as better explained below, are fulfilled by an electric generator as defined in claim 1, which consists of a drive shaft with a longitudinal shaft, designed to be connected to an external power source having a predetermined rotational force, a rotary electric machine with synchronous resistance having a stator and a cross-laminated rotor, and an output shaft operatively connected to said drive shaft to generate electricity by a rotational force having a predetermined determined amplitude during operation, electrical connection means for injecting into the network the electrical energy generated by the electrical machine and control means designed to adjust the electrical and dynamic parameters of the electrical machine.

The generator is characterized so that the stator has an even number of longitudinal grooves for each pair of bars, the rotor has a plurality of longitudinal slots that define an even number of magnetically equivalent slots, where the number of grooves is different from the number of equivalent slots multiplied by an integer, where the difference between the number of grooves and the number of equivalent slots is different from zero, +2 and -2.

The generator is further characterized by the additional features of claim 1.

With this particular configuration, a generator can be provided that has particularly high electrical performance despite its use of smaller control means, and this also ensures high durability and lower maintenance requirements.

Advantageous embodiments of the invention are defined in accordance with the dependent claims.

Short description of the pictures

Further features and advantages of the present invention will be apparent upon reading the detailed description of several assumed, non-exclusive embodiments of a generator having a synchronous resistance electric machine, which are described as non-limiting examples with the aid of the accompanying figures in which: FIGURE 1 is a schematic perspective view of the generator of the present invention;

FIGURE 2 is a detached front view of the electrical machine forming part of the generator of the present invention;

FIGURE 3 is an enlarged view of the detail from Figure 2;

FIGURE 4 is a detail perspective view of this generator as shown in Figure 1; FIGURE 5 is a side view of the electrical machine that is part of this generator in the first configuration;

FIGURE 6 is a side view of the electrical machine that is part of this generator in another configuration;

FIGURE 7 is a frontal view of the electrical machine that is part of this generator in the third configuration;

FIGURE 8 is a side view of the electric machine of Figure 7;

FIGURE 9 is a schematic side view detailing the generator of the present invention.

A detailed description of the assumed implementation

Referring to the figures above, the generator of the invention, generally referred to as numeral 1, can be used in systems for producing electricity from fossil and chemical energy sources, or renewable energy, such as wind or water energy. The figures show, as non-limiting examples, a generator 1 using a renewable energy source, specifically an air turbine 2. It will be appreciated that the air turbine 2 can be replaced with a water or steam turbine, that is, a fossil fuel internal combustion engine.

The wind generator 1 can be used both in small and medium energy systems, such as civil and industrial installations, as well as in large energy systems in terrestrial or onshore or off-shore installations.

Moreover, the generator 1 may have a horizontal or vertical shaft design and may be entirely housed in a housing, not shown, located at the end of the tower, also not shown.

The generator 1 consists of a drive shaft 3 that rotates around the longitudinal axis L and is adapted to be connected to an external energy source.

In the wind generator 1, the energy source can consist of a turbine 2 having one or more blades, directly attached to the drive shaft 3, as in the schematic configuration in Figure 1, or to a different shaft operatively connected to the drive shaft 3 to transmit motion from the turbine 2 to it.

As is known, the turbine 2 consists of a propeller 5 with blades 4, the pitch angle of which can be fixed or designed to change according to the force of the wind, for example, by using suitable moving means, not shown, connected to each of the blades 4.

Furthermore, the generator 1 may be rotatably supported by a support structure, not shown, to rotate about a vertical axis defined by a support tower, not shown, thereby allowing the wind turbine 2 to be continuously oriented downwind even when the wind changes its direction.

Therefore, the drive shaft 3 of the generator 1 is connected to the ejected shaft 6 of the rotary electric machine 7 of the synchronous resistance type.

In particular, the electric machine 7 consists of a stator 8 having at least one pair of bars and a plurality of longitudinal grooves, generally referred to as 15, and a cross-laminated rotor 9 having a splined shaft 6.

Thus, the electric machine 7 can generate electricity with a predetermined rotational force during operation.

For example, the drive shaft 3 can be connected to the ejected shaft 6 of the electric machine 7 by the coupling means 10.

In this configuration, the speed of rotation of the drive shaft 3 substantially coincides with the speed of rotation of the output shaft 6 of the electric machine 7.

In an alternative configuration of the invention, a multiplier device, not shown, can be inserted between one end 11 of the drive shaft 3 and one end 12 of the output shaft 6, in order to increase the rotational speed of the output shaft 6 compared to the speed of the drive shaft 3.

The multiplier device may be selected from currently available devices and may include kinematic transmission means, not shown, such as gears, epicyclic gears or drive belts.

This configuration can be used in a generator 1 with an electric machine 7 operating at a rotational speed significantly higher than that of the drive shaft 3.

The generator 1 further consists of electrical connection means 13 for injecting the electrical energy generated by the electrical machine 7 into the network and control means 14 for adjusting the electrical and dynamic parameters of the electrical machine 7.

Advantageously, the stator 8 has an even number of longitudinal grooves 15 for each pair of bars and the rotor 9 has a plurality of adjacent longitudinal slots, generally referred to as 16, defining an even number of magnetically equivalent slots.

The grooves 15 can be essentially longitudinal, and their length can essentially coincide with the length of the stator 8.

In the illustrated configuration of the invention, the stator 8 has two pairs of bars and twenty-four grooves 15.

However, it will be understood that the pairs of bars and thus the grooves 15 may also be provided differently in number, without limiting the scope of the present invention.

The rotor 9 is assumed to be composed of a plurality of disc plate elements 17 which have a predetermined thickness s, and which are arranged in a longitudinal connection to each other and are an integral part of the ejected shaft 6.

The inner diameter d of the disc plate elements 17 can essentially coincide with the diameter of the ejected rotor shaft 9.

Each of these disc plate elements 17 has a plurality of longitudinal slit slots 16, which are distributed in substantially identical arrangements in each of the elements.

Advantageously, the slots 16 can have an elongated curved shape, symmetrical in diameter with the relevant disc plate element 17, with the end portions 18, 18' close to the edge 19 of the disc element 17, so that each slot 16 can limit at least one pair of ribs 20, 20' on that edge 19.

The grooves 16 of the rotor 9 are configured so that, during the operation of the electric machine 7, the magnetic field in the stator 8 will saturate the fins 20, 20' which, under essentially magnetic conditions, will operate as if the disc plate element 17 has an additional slot on it.

Further saturation areas are located on the central parts 21 of the slots 16 of the rotor 9, which are placed near the peripheral edge 19 of the disc plate element 17.

In particular, each of these slots 21 near the edge 19 have an additional pair of ribs 22, 22' defining magnetically equivalent slots.

Therefore, the total number of magnetically equivalent slots will not be equal to the number of ribs thus defined.

According to a peculiar aspect of the invention, the number of nrmagnetically equivalent slots and the number of nsslots 15 are selected according to a previously determined ratio, to minimize the rotational force in the electric machine 7 during operation.

In particular, the number of n-slots 15 is different from the product of equivalent slots by an integer m, and the difference between the number of n-slots 15 and the number of n-equivalent slots is different from 0, +2 and -2.

By default, the number of non-equivalent slots is also greater than 6.

Regarding the above ratios, a particular configuration of the invention can be given, as shown, in which the rotor 9 consists of a plurality of disc plate elements 17, with a ratio r between their inner diameter d and outer diameter D ranging from 0.4 to 0.8.

In particular, this ratio r can be 0.45 or more and, also, the number of n-equivalent slots can be equal to the number of nsgrooves 15 reduced or increased by four units.

In a further configuration, the generator 1 may include a plurality of permanent magnets, generally referred to as 23, connected to the rotor 9.

Permanent magnets 23 can be obtained by sintering base materials containing neodymium (Nd), iron (Fe) and boron (Bo) to obtain a low specific gravity while simultaneously maintaining high magnetic properties (properties), compared to conventional magnets, such as ferrite magnets and the like.

However, it should be understood that conventional ferrite magnets may also be used.

Such magnets 23 can be provided in such a number that they have a smaller magnetic mass than permanent magnets used in electric machines with permanent magnets having approximately the same strength.

Presumably, the magnetic mass of the permanent magnets 23 can be in the range from 30 Kg to 150 Kg, preferably from 50 Kg to 125 Kg.

In particular, according to an exemplary, non-limiting configuration of the invention, a generator capable of generating 3 MW of electric current at 1000 revolutions per minute may comprise an electric machine 7 having permanent magnets with a magnetic mass of 100 Kg to 125 Kg.

In generator 1 designed to generate 1 MW of electric current, the values can be reduced by a third compared to the above mentioned.

Conveniently, the permanent magnets 23 may be located in one or more predetermined portions 24, 24', 24", 24'" of the disc plate element 17 of the rotor 9.

Each element of the disc plate 17 will receive a permanent magnet 23 with one or more pairs of magnetic poles.

Presumably, but without limitation, the permanent magnets 23 will be in the central portion 24, 24', 24", 24"' of the disc plate element and located at least one adjacent slot 16, as shown, to form a rotor 9 with embedded magnets.

Nevertheless, the permanent magnets 23 may be inserted into multiple adjacent slots 16 in different rows, so as to be arranged relative to each other.

Moreover, the permanent magnets 23 can be equally distributed along the axis L of the rotor 9.

Also, the number of permanent magnets 23 will be selected considering the reduction in electrical specification and/or power specification of the control means 14 compared to the control means 14 of electric machines 7 with permanent magnets 23 having approximately the same power.

For example, the permanent magnets 23 can be designed to generate a magnetic flux in the range of 10% to 20% of the value of the magnetic flux generated by the electric machine 7 of the prior art with permanent magnets 23, with the same power.

The special configuration of the electric machine 7 can reduce the electrical and power specifications of the control means 14 in a value that is in the range of 20% to 30% compared to the control means 14 used in the electric machines 7 with permanent magnets 23.

In particular, the control means can be designed to control the electric machine 7 with an electric current ranging from 400 A to 1000 A, and preferably from 500 A to 800 A.

The control means 14 of the electric machine 7 include a circuit 25 which is electrically connected to the stator 9 in order to adjust the electric and dynamic parameters of the electric machine 7.

For example, the control means 14 include an inverter 26, which is designed to maintain the rotational speed of the output shaft 6 of the electric machine 7 at a predetermined value.

Presumably, the inverter 26 is designed to control the current rotational speed communicated to the output shaft 6 by an external source.

The rotation speed of the ejected shaft 6 can be changed in the range between the previously determined minimum and maximum values.

Furthermore, the inverter 26 can be designed to control the rotational speed of the output shaft 6 periodically at predetermined time periods.

Any deviation of the value of such a speed in relation to the previously determined value will start the inverter 26 and the bundle of certain electrical parameters of the control signals will thereby be transmitted to the electrical machine 7.

Such changed control signals will allow the electric machine 7 to change operation and keep the generated power essentially constant.

Furthermore, in a configuration of the invention, not shown, a programmable logic unit may be provided, which is connected to the control means 14 and may also be connected to an external source, e.g., a wind turbine 2 .

For example, in the case of the wind generator 1, the programmable logic unit can keep the power delivered by the electric machine 7 constant even though the wind power changes, by operating the inverter 26 and the turbine 2 in a simultaneous and synchronized manner.

The programmable logic unit can change the operating point of the electric machine 7 through the operation of the inverter 26 and can also change the wind work on the drive shaft 3 by working on the blades 4 of the turbine 2, eg by changing their pitch angle.

Moreover, the control means 14 may also include a converter element 27, which is designed to change the electrical parameters associated with the generated energy of the electric machine 7, thus allowing its injection into the external transmission network R.

Conveniently, the operating point of the electric machine 7 can be set by a string of electrical quantities associated with the signals given by the control means 14 to the stator 8.

In a particularly advantageous configuration, as shown in Figures 6 to 9, the electric machine 7 may comprise an outer casing 28 comprising the stator 8 and rotor 9 assembly with an interspace 29 designed to allow the passage of cooling air along a loop path 30 passing through the interspace 29, the adjacent slots 16 of the rotor 9 and the interspace 31 between the rotor 9 and the stator 8.

An intermediate space 29 may be formed near the peripheral edge 32 of the stator 8 to facilitate the heat exchange of cold air from it with the environment.

The loop path 30 so configured will allow the stator 8 and rotor 9 assembly to be cooled by the unforced circulation of the cooling air flow.

Furthermore, the generator 1 can include air cooling means 33 driven by the rotor 9.

Conveniently, the cooling means 33 controlled by the rotor 9 can also be provided in electrical machines 7 with synchronous resistance which are not used as generators 1 of electrical energy and do not have to comply with the mathematical relationships associated with the number of nslots and the number of nrequivalent slots as mentioned above.

According to a special feature of the invention, the cooling means 33 may consist of one or more moving vanes, generally referred to as number 34, coaxial with the rotor 9, at least on one and preferably on both ends 35, 35' of the rotor 9, where the vanes 34 are facing at least one of the ends 35, 35' to supply the cooling air flow.

In an assumed, non-limiting configuration of the invention, as shown in the figures, the rotor 9 may consist of a pair of driving vanes 34, each at one end thereof 35, 35', to increase the flow of air supplied to adjacent slots 16.

Each driving vane 34 may be located at a predetermined distance from a corresponding end of the rotor 35, 35'. That distance can be identical or different for the two vanes 34.

In a further configuration of the invention, not shown, the individual driving vanes 34 can be located at the ends 35, 35' of the rotor 9 by ring-shaped fastening elements, not shown, which are connected to the ejected shaft 6 of the electric machine 7.

Furthermore, each driving vane 34 may include a plurality of blades, generally referred to as 36, which are specially shaped towards the end of the rotor 9 towards which they face.

The blades 36 can be variously shaped to generate a flow of air that flows into one end 35, 35' of the rotor and exits at the opposite end 35', 35.

The two driving vanes 34 can have the same number of blades 36 or their different number, so that different air flows can be supplied to each end 35, 35' of the rotor 9.

Conveniently, the cooling means 33 may comprise an air cooling conduit 37 in fluid communication with the outer housing 28 at one or both ends 35, 35' of the rotor 9 along the path 30.

In the configuration of the figures, the conduit 37 may be closed and contains the adjacent slots 16 of the rotor 9, the intermediate space 29 and the ends 35, 35' of the rotor 9.

This configuration provides a higher cooling air flow compared to the flow generated by uninduced circulation.

Advantageously, as shown in Figure 8, the cooling means 33 may comprise a heat exchanger 38 in fluid communication with the intermediate space 29, inside or outside the latter, for the purpose of cooling the air.

The exchanger 38 may be of the air-to-air or air-to-fluid type and cooling air may be supplied through two openings 39, 39' at the respective longitudinal ends 40, 40' of the stator 8.

Advantageously, the cooling means 33 may include one or more pumps, generally indicated by numeral 41, driven by the ejected shaft 6 to supply respective cooling loops, generally indicated by numeral 42, connected to the stator 8, the control means 14 and possibly to the heat exchanger 38, each separately.

In this configuration, the pumps 41 are only started during the movement of the ejected shaft 6 and will not work when the latter is not rotating or has a rotation speed lower than a previously determined value, that is, insufficient to start them.

Furthermore, each pump 41 can supply the same fluid to all cooling circuits 42 or supply different fluids to one or more cooling circuits 42 .

Conveniently, the flow rate of each pump 41 can be selected according to the amount of fluid required for each circuit 42 .

The configuration thus obtained will be particularly efficient and will avoid unwanted energy losses in the cooling circuit. Also, it will allow the generator 1 to be compact, while reducing its overall weight.

Further, the stator 8 may be of the toothed coil type 43, with the stator windings, generally referred to as 44, of shorter shaft length.

The reduced length of the stator winding 44 will allow the conduit 37 to have a greater width and the dimension 1 of the stator 8 to be smaller than in a conventional stator, which will lead to a reduction in the longitudinal dimensions of the generator 1.

In this configuration, the stator 8 of the electric machine 7 will require a smaller amount of conductive fiber, e.g. made of copper, than conventional stators 8.

The Type 43 Serrated Coil Stator 8 is lighter in weight and more cost-effective than a conventional Stator 8.

The above disclosure clearly shows that the invention fulfills the objects to which it is directed and in particular fulfills the requirement of providing a generator that has high electrical performance while being cost effective and having reduced dimensions and weight. The generator of the invention is susceptible to numerous changes and variations within the scope of the inventive concept disclosed herein in the appended claims. All these details can be replaced by other technically equivalent parts, and the materials can vary according to different needs, without going beyond the scope of this invention.

While the generator is described with particular reference to the accompanying figures, the reference numerals in the description and claims are used only for better understanding of the invention and are not intended to limit in any way the scope of protection claimed.

Claims (8)

1. Electric energy generator that is driven by an external energy source, such as wind, which consists of: - drive shaft (3) with a longitudinal axis (L), designed to be connected to an external energy source and which has a predetermined rotational force; - rotary electric machines (7) with synchronous resistance consisting of a stator (8) and a transverse laminated rotor (9), and an ejected shaft (6) operationally connected to the specified drive shaft (3) in order to generate electricity with a rotational force of a predetermined amplitude during operation; - means for electrical connection (13) in order to inject into the network (R) the electrical energy generated by the specified electrical machine (7); - control means (14) designed to adjust electrical and dynamic parameters of the specified electric machine (7); wherein said stator (8) has an even number (ns) of longitudinal grooves (15) for each pair of bars and said stator (9) has a plurality of longitudinal slots (16) defining an even number (nr) of magnetically equivalent slots, characterized in that said number (ns) of grooves (15) is different from the number (nr) of equivalent slots multiplied by an integer (m), where the difference between said number (ns) of grooves and said number (nr) of equivalent slots is different from zero, +2 and -2, where said rotor (9) is formed by a plurality of disk plate elements (17) placed longitudinally side by side, wherein said plurality of longitudinal slots (16) for passage where are each formed in each of said plurality of disk plate elements (17), wherein each of said disk plate elements (17) is substantially annular, with an outer diameter (D) and a central through hole within the diameter (d) that is designed to be connected to said ejected shaft (6), wherein the ratio (r) between said inner diameter (d) and said outer diameter (D) of each annular element of the disc plate (17) is between 0.4 and 0.8. 2. The generator according to claim 1, characterized by the fact that the stated number (nr) of equivalent rotor slots (9) is greater than six (nr> 6). 3. The generator according to claim 1, characterized by the fact that for each of the mentioned ring elements of the disc plate (17), the mentioned ratio (r) is essentially equal to 0.45 and the number (nr) of equivalent slots is defined by the formula: where n is the number of said grooves (15) of said stator (8). 4. The generator according to claim 1, characterized in that it contains a plurality of permanent magnets (23) inserted into one or more of said longitudinal slots (16) of said rotor (9). 5. Generator according to claim 1, characterized in that said permanent magnets (23) consist of materials selected from the group consisting of neodymium (Nd), iron (Fe) and boron (Bo) and have a total magnetic mass between 30 Kg and 150 Kg for a generator having a maximum power between 1 MW and 3 MW. 6. Generator according to claim 5, characterized in that said control means (14) are set to control said electric machine (7) with electric currents between 400 A and 1000 A, preferably between 500 A and 800 A. 7. Generator according to claim 1, characterized by the fact that said control means (14) consist of a circuit (25) electrically connected to said stator (8) in order to adjust the electrical and dynamic parameters of said electric machine (7). 8. The generator according to claim 1, characterized by the fact that said stator (8) has stator windings (44) with a smaller longitudinal extension than conventional stators in such a way as to reduce the longitudinal dimensions of the generator (1).